TOKYO - Rescue teams searched through matchstick rubble Saturday for thousands of people missing in flooded areas of northeastern Japan, beginning one of the most complex relief efforts in history.

A day after the 8.9-magnitude earthquake and massive tsunami, entire towns remained impossible to reach and some were feared to be wiped off the map. Most estimates put the death toll at 1,700, but news services quoted police in Miyagi Prefecture - one of the hardest-hit areas - as saying they expect the number to exceed 10,000 in that region alone.

About 200,000 people are living in temporary shelters. A strip of Japan's main Honshu island has almost no electricity, with scarce means to communicate. Many shelters do not have heat. Survivors at an elementary school in the devastated coastal town of Minamisanriku used chalk to write their message on a dirt playground: "SOS."

An explosion at a nuclear power plant in Fukushima Prefecture and concerns about potential radiation leakage prompted evacuations within a 12.5-mile radius. As many as 160 people near Fukushima's nuclear plants have been exposed to radiation.

In other areas north of Tokyo, closest to the epicenter of Friday's earthquake, witnesses said the massive wave had swallowed and chewed up entire neighborhoods. Attempts to reach those stranded, trapped or short on supplies were complicated by damage to the roads and rail lines.

Roughly 9,500 people in Minamisanriku - a town of 17,000 in Miyagi Prefecture - remain unaccounted for, the Kyodo news agency reported, citing local government officials. Phone lines are dead at schools. Footage taken by helicopters allowed for a before-and-after comparison: Where there was once a fishing and tourist village, there is now a lake, with only a few buildings poking out from the murky black.

"Even the medical relief is going to be a longtime battle," said Toshikazu Yamamoto, a Japanese Red Cross official in charge of disaster relief. "This earthquake is much larger than the Kobe earthquake [in 1995]. And Kobe took 10, 15 years to recover, and it actually hasn't recovered completely even now. Recovery from this earthquake is going to take a long, long time."

Attempts to map out the damage were only beginning as Japan dispatched 50,000 troops to the disaster zone. The coastal town of Rikuzentakata, in Iwate Prefecture, was entirely submerged by water, according to local authorities. One TV reporter who arrived at Iwaki, in Fukushima Prefecture, said the town was gone.

A derailed train in Miyagi Prefecture, closest to the quake's epicenter, was seen waylaid against the side of a house. There were no reports on the whereabouts of passengers.

With roads pretzeled and fuel in high demand along the undamaged routes heading north, the government will depend on ships and aircraft for the rescue work. Japan is sending 195 aircraft and 25 vessels to the disaster area, according to Kyodo. U.S. ships will join them for search-and-rescue missions.

Japanese power companies warned of severe outages in the coming days, with energy sources in diminished supply.

On Saturday, Japan's northeastern coastline, viewed from above, had the look of a dark scar. The fiercest wave sent a wall of water upward of 20 feet high toward the shoreline, and it spread some six miles inland. At 6 a.m. local time, Prime Minister Naoto Kan surveyed the area by helicopter. Those on the ground told of screams from trapped survivors, houses turned to splinters and overtaxed hospitals and shelters.